Jeff Horwich: First up, we've got an exclusive on a new investigation into the hundreds of thousands of deep wells around the country -- filled with industrial waste. They might not be as safe as we think they are.

Abrahm Lustgarten is a reporter with ProPublica. Good morning.

Abrahm Lustgarten: Thank you for having me.

Horwich: First, tell us about these underground injection waste wells -- who uses them and what are they supposedly good for?

Lustgarten: Well there's a couple different kinds, but basically everybody uses them -- from the pharmaceutical and the chemical manufacturing industry, to the oil and gas industries, to your neighborhood gas station. They basically dump waste to varying depths underground, out of sight, out of mind. The most toxic contaminants are put deep underground, anywhere between 1,500 feet and 10,000 feet underground.

Horwich: And what's the reason that we take this waste and put it so far underground?

Lustgarten: The thinking is that it gets buried deeply below layers of rock that provide a seal forever. One of the regulatory thresholds is that fluids will stay there for 10,000 years. So the waste goes down into porous layers of rock or aquifers that are never going to used for drinking water supplies, and just basically stays trapped up down there forever and we never hope to see it again.

Horwich: The upshot of your investigation is that many of these wells may be leaking and we might not even know about it. If they leak, what happens?

Lustgarten: Well, it's not entirely clear what happens. There's an example I explore in southern Ohio where a hazardous waste well did leak, and it took 20 years for the contaminants to move up through the rock, about 1,400 feet. And that's the point where researchers had been investigating what had happened with that well. The question is: How long does it take those contaminants to continue to move -- will they continue to move? But if they were to get into people's water supplies, then it would ruin that water supply. But the challenge is: How will people know it? Will they taste it, will it be detected in some other way?

Horwich: If in fact we cannot rely on injection waste wells like we thought we could, what are the implications for industry?

Lustgarten: Well it's huge. It's the most important way to dispose of liquid waste. The consensus may still be that this is the best alternative that we face -- we just perhaps need to evaluate the risks, understand what those risks might be better. Recycling is an alternative that's more expensive. Producing the less waste is the thing that sources tell me should be our ultimate goal with the threats of waste disposal in mind -- the greater cost is perhaps worth the effort to simply produce less material that needs to be put underground.

Jeff Horwich is the interim host of Marketplace Morning Report and a sometime-Marketplace reporter. He is the former host of "In The Loop" from Minnesota Public Radio and a former business and economics correspondent for MPR. He is a graduate of Duke University and has a Master's in applied...